Slips for supporting drill pipes in well-boring apparatus



Sept. 7, E. PEARSON ET AL SLIPS FOR SUPPORTING DRILL PIPES IN WELLBORING APPARATUS Filed Nov. '7, 1925 2 Sheets-Sheet 1 1,643,750 P 1927'E. c. PEARSON ET AL SLIPS FOR SUPPORTING DRILL PIPES IN WELL BORINGAPPARATUS Filed Nov, '7, 1925 2 Sheets-Sheet 2 Patented Sept. 27, 1927.

UNITED STATES 1,643,750 PATENT OFFICE.

EDMUND CURTIS PEARSON AND JAMES CHILDS, OF WESTMINSTER, LONDON, ENGLAND,ASSIGNORS TO VICKERS LIMITED, OF WESTMINSTER, ENGLAND, A BRITISH COM-PANY.

SLIPS FOR SUPPORTING DRILL PIPES IN WELL-BORING APPARATUS.

Application filed November 7, 1925, Serial No. 67,480, and in GreatBritain November 27, 1824.

This invention relates to slips for supporting drill pipes inwell-boring apparatus.

In one form of apparatus for well-boring in which the necessary power isderived from a rotary machine, the boring bit or tool is attached to thelowest one of a number of connected lengths of drill' pipe, which drillpipe is in turn screwed to a drive stem of square cross section. Thisstem passes through a drive bushing fitted into a master bushing, whichlatter is in turn fitted into a recess in the table of the rotarymachine. The whole length of drill pipe and the square stem can beraised and lowered, being for example suspended by a wire rope from ablock at the top of a derrick provided with hoisting gear. As thedrilling progresses it becomes necessary from time to time to addfurther lengths of drill pipe to the end of the connected succession orstring of pipesin the hole. To enable this addition to be accomplished,the square drive stem is raised along with the drive bushing, bringingthe string of pipes up through the table of the machine. It is necessaryto support the length of pipes in the hole by means other than theoverhead block, and for this purpose fittings called slips made invertically divided halves are placed in a tapered hole in the masterbushing, the said sli s having horizontal teeth in contact with e It isfrequently found, however, that the drill pipes arev not truly circularon their outer' circumference, and it is anobject of this invention toensure that the total weight of the string of pipes shall be evenlydis-- tributed notwithstanding the occurrence of such irregularities,thereby avoiding damage to the pipes.

According to this invention the ta ered annular slips, which are asusual ra ially divided into halves, or otherwise into a plurality ofindependently movable members, have on their inner surfaces inclinedrecesses, wherein segments of hardened steel are capable of sliding upand down, the said segments projecting eyond the inner surfaces of theslips and having horizontal or helical teeth adapted to grip the drillpipe to resist the descent thereof. When the slips are lifted eachsegment is pulled to the top of Rs travel by a boltpassmg through areand when the slips are lowered into the tapered hole in the table ofthe rotary drill ing machine so as to surround the drill pipe, eachsegment is free to fall by gravity to the bottom of its travel, or sofar as is permitted but to their maximum radius, thereby freeingthemselves from the pipe.

it has previously been proposed, in a pipe lifter having hinged jawsclosing on the pipe, to provide toothed segments separately adjustablein inclined recesses in the jaws, but these segments were set by screwsto suit a variable but known diameter of pipe instead of beingself-adjusting by gravity as in the present invention, and were drivenupwards andsupported by springs, instead of being lifted in unison by alifting plate when disengaging the pipe.

In order that the said invention may be clearly understood and readilycarried into effect, the same will now be described more fully withreference to the accompanying drawings, in which Figure 1 representsinelevation one slip of .a pair, provided with horizontally toothedsegments.

- Figure 2 is a plan of the said slip.

Figure 3 is air elevation of a pair of slips viewed from a direction atright angles in relation to the view in Figure 1, a portion of one. ofthese slips being represented in section on the line 33 in Figure 2.

Figure 4 re resents'in elevation a slip provided with he ically toothedsegments.

The segments B may be prevented bya ref taining plate C, secured to thetops of the slips, from rising out of the tapered slots .D which aremachined in the bore of the slips. Above the retaining plate is alifting plate E provided with one or more handles F, and

olts or screws G passing throu h elongated clearance holes H in both thelifting plate E and the retaining plate C are screwed into each of thesegments, so that when the slips are raised from the ground by the sandhandle the segments B are thereby automatically pulled to the tops ofthe slots D in the slips. The slips are then lowered by hand into thetapered hole in the master bushing'and embrace the'pipe, and the handleF is then released. If the pipe is truly circular and of the correctsize the segments B will remain in their highest positions in the slots;but should the pipe not be truly circular certain segments will falldown wards and inwards until all the segments are in contact with thepipe. The string of drill pipes is then slightly lowered, when the teethof the segments bite into the metal of the pipe and support the wholeweight of the string of pipes.

When the additional length of drill pipe has been attached to the stringof pipesin the hole the square drive stem is again attached to thestring of pipes and the full weight taken on the wire rope. .The wholestring of pipes is then raised a short distance by means of the hoist onthe derrick. This causes the toothed segments B to press against theretaining plate C so that the slips are lifted ofl their seating in themas ter bushing, and the slips can then be re-' moved by hand.

Means are rovided to prevent the toothed segments B rom falling down thewell in the event of the lifting screws G breaking. For example a pin J(Figure 3) may be screwed into the back of each toothed seg ment B itshead projecting into a groove in the sli and a stop K is cast acrosseach groove, the pin J being located an appreciable distance above thestop so that the normal movements of the segments are not affectedthereby.

By the use of slips according to this invention the following advantagesare obtained, in comparison with slips having integral teeth :-Thetoothed segments working in tapered slots are free to, adjust themselves to the irregularities of the drill pipe, so that the load isevenly distributed between all the segmeins. These segments can neaavsoeasily be removed and replaced, thus eliminating the difficulties causedby dull'slips and loss of time in ire-sharpening the teeththereof. It isonly necessary that the segments themselves should be made of hardenedsteel, .as the body of the slips may be of a material which is cheaperand more easily machined.

In the following claims, the expression substantially horizontal teeth.must be understood to include teeth which are'actually horizontal asillustrated in Figure 1, or helical as illustrated in Figure 4.

What we claimQand desire to secure by Letters Patent of the UnitedStates is In well boring apparatus arouate' slips adapted to be fittedinto a tapered hole in the tajole of a rotary drilling machine fortemporarily holding drill pipes in one position, each of said slipsbeing provided with a pluralityof independently movable members, saidmovable members being composed of segments of hardened steel, capable.of sliding up and down in inclined recesses on the inner surfaces of theslip members, each 1 segment projecting beyond the inner. surface of itsslip member and having substantially horizontal teeth adapted to gripthe drill pipe to resist the descent thereof, a retaining plate securedto the top of each slip member, a lifting plate located above saidretaining plate and having a handle, bolts passing through elongatedclearance holes in both the lifting plate and retaining plate, saidbolts being secured to the segments, whereby the segments areautomatically pulled to the top of their travel when said handle israised to lift the slip member, and said bolts being of such length asto allow each seg-.

ment to fall by gravity independently of adjacent segments when saidhandle is released until all the segments bear against the pipe, wherebythe load is distributed over all said segments irrespective of whetherpipe be truly circular.

EDM. C. PEARSON. JAMES CHILDS.

the outside of the

